Method and apparatus for molding containers

ABSTRACT

The molding of an angular container with an open top and with sidewalls which are outwardly inclined or provided with an outwardly projecting rim on their free edges in an upside-down position on a stationary mold core by means of horizontally movable dies and a vertically movable bottom-forming die of a mixture of a comminuted fibrous material and a hot-setting binder, wherein the dies are made of a shape so that in their compressing position the front ends of their adjacent sides overlap each other, whereby the dies not only mold the container itself but also compress and cure the mixture which has been filled into the area between each edge of the core and two adjacent retracted dies so as to form thin solid strips which extend along and project outwardly from edges of the molded container and which are to be broken off after the dies have been retracted and the container has been lifted out of the mold.

United States Patent [72] Inventors Edmund Monk;

Herbert Haas; Gerd Weinberg, all of Oberstenfeld, Germany [21] Appl No.774,747 [22] Filed Nov. 12, 1968 [45] Patented July 6,1971 [73] AssigneeFurnler-und Sperrholwerk, J. F. Werz Jr.

R. G. Obersteufeld, Wurttemberg, Germany [54} METHOD AND APPARATUS FORMOLDING CONTAINERS 13 Claims, 4 Drawing Figs.

[52] 0.5. CI 18/5, 18/l6,264/122 [Sl] Int. Cl 829g 7/00 [50] FieldotSearch 18/5, 5 P, 16, DIG. 26; 264/161, 122

[56] References Cited UNITED STATES PATENTS 2,583,441 1/1952 Palmer18/16M Primary Examiner- Richard J. Herbst Attorneys-Leslie G. Nollerand John M. Crawford ABSTRACT: The molding of an angular container withan open top and with sidewalls which are outwardly inclined or providedwith an outwardly projecting rim on their free edges in an upside-downposition on a stationary' mold core by means of horizontally movabledies and a vertically movable bottom-forming die of a mixture of acomminuted fibrous material and a hot-setting binder, wherein the diesare made of a shape so that in their compressing position the front endsof their adjacent sides overlap each other, whereby the dies not onlymold the container itself but also compress and cure the mixture whichhas been filled into the area between each edge of the core and twoadjacent retracted dies so as to form thin solid strips which extendalong and project outwardly from edges of the molded container and whichare to be broken off after the dies have been retracted and thecontainer has been lifted out of the mold.

PATENTED JUL 6 1911 I I I FlG.2

Fl G.l

PRIOR ART FIG.3

PRIOR ART INVENTORS EDMUND MUNK HERBERT HAAS %2RD WEINBERG ATTORNEYSMETHOD AND APPARATUS FOR MOLDING CONTAINERS The present inventionrelates to a method and an apparatus for producing containers by moldingthem under heat and pressure of a mixture of comminuted fibrousmaterials, for example, wood or bagasse, and a hot-setting binder, forexample, a urea formaldehyde resin or a melamine resin. The inventionfurther relates to the production of containers of such materials thewalls of which are either outwardly slightly inclined toward their upperrim or extend substantially vertical to the container bottom and have anupper rim of a larger circumference than that of the bottom so that ineither case the rim of the container projects laterally over the bottom.

Containers of this type are generally produced in an upsidedown positionby applying the material about a stationary core of a suitable shape andby then compressing and simultaneously heating this material by means ofa downwardly movable die and a suitable number of laterally movabledies. For removing the molded container from the mold in the upwarddirection thereof these dies are retracted for a sufficient distancefrom the core. If the container has walls which are slightly inclinedtoward the outside or extend vertically but have an outwardly projectingrim on their upper edges the difficulty arises that the comers of theupper edge of the container which projects laterally over the bottom andforms the lowest part of the container in the mold since the containeris molded in an upside down position lie underneath the stationarylateral guides of the dies which therefore prevent the removal of thecontainer even if the lateral dies are sufficiently retracted. For thisreason it has previously been necessary to cut off the downwardlyextending rectangular comer of each of these stationary guide elementsbetween the guide surfaces for the adjacent dies, i.e. the comer ofguide element facing an upright corner of the molded container, so thatin place of this corner of the guide element a surface is formed whichextends obliquely to each of the adjacent guide surfaces and is set backso far from the corner of the molded container that the projecting rimof the latter may be moved easily past these oblique surfaces when thecontainer is lified out of the mold. By cutting of? the corners of eachof the stationary guide elements, a chamber of a triangular crosssection is formed in which this material also collects when the dies areretracted and the material is filled into the mold. During the followingcompression of the material so as to form the walls of the container,the material in these chambers although not compressed is neverthelessheated so that the binder therein is cured and this material forms aloose crumbly residue which, when the dies are subsequently retractedand the container is withdrawn from the mold, falls into the mold. Thismaterial must then be completely removed from the mold before the nextmolding operation can be carried out. This is a difficult andtime-wasting procedure and there is also always the danger that the moldmight not be cleaned sufficiently with the result that the nextcontainer to be molded will be defective.

It is an object of the present invention to eliminate this disadvantagein the production of containers of the type as previously describedwhich are made of a compressed mixture of vegetable fibers and ahot-setting binder. This object is attained according to the inventionby not merely heating but also compressing the excess material which hascollected in the necessary chamber along the edges between two adjacentsurfaces of the stationary guide element when the mold is filled so thatalong the upright corner of the container a solid rod-shaped, outwardlyextending projection is formed. Another feature of the inventionconsists in compressing this rod-shaped projection so as to be connectedonly by a very thin web to the corner of the container which extendsparallel thereto. Since this projection including this thin web is ashighly compressed and cured and has the same solidity as the walls ofthe container, it may be easily and completely broken off the comer ofthe container along the thin connecting web.

The above mentioned as well as additional features and advantages of thepresent invention will become further up parent from the followingdetailed description thereof which is to be read with reference to theaccompanying drawings, in which FIG. I shows a horizontal section whichis taken along the line H of FIG. 3 and illustrates a mold as employedprior to this invention in its compressed position for producing acdntainer of the type as described.

FIG. 2 shows a similar horizontal section which is taken along the linell-ll of FIG. 4 and illustrates a mold according to the presentinvention.

FIG. 3 shows a vertical section of the known mold according to FIG. 1;while FIG. 4 shows a similar vertical section of the mold according tothe invention as shown in FIG. 2.

In orderto explain the present invention more clearly, it is advisablefirst to describe briefly the method which has previously been carriedout for producing such containers. FIG. 1 shows a horizontal sectionwhich is taken along the dot-anddash line I-l of FIG. 3 transverselythrough a mold as previously employed and illustrates an upright cornerof the container when the lateral dies 4 and 5 are in the fullycompressed position, while the dash lines 4' and 5' indicate theposition of these dies when retracted. The numeral 1 designates thewalls of the compressed container and the numeral 2 the stationary coreof the mold around which the container is molded. The lateral dies 4 and5 are movable in the direction of the arrows a and b along the guidesurfaces of the stationary guide ele ment 3 of the mold. The dotted line1' indicates the upper edge of the container which in the mold forms thelower edge since the container is molded in an upside-down position. Thewalls of the container are therefore to be slightly inclined toward theoutside. Since the rectangular comer of the stationary guide element 3which faces the comer ll" between the two walls 1 of the container wouldprevent the finished container from being removed from the mold, it haspreviously been necessary to cut off this comer of the guide element 3at an angle of. 45 so that an oblique surface 3 was formed. When thedies 4 and 5 are in the compressing position, this surface 3' and thesidewalls of dies 4 and 5 are retracted to permit the molding mixture tobe filled into the area between the core 2 and the dies, this chamber 6is likewise filled with the molding material. Although this material inchamber 6 is likewise heated during the compressing operation of thedies 4 and 5 it will not be compressed by the latter but form a loosecrumbly residue in chamber 6. When the compressing operation iscompleted and the dies 4 and 5 are retracted from the finishedcontainer, this crumbly material will fall to the bottom of the mold andmust then be carefully and completely removed therefrom since otherwisethe next container will be defective.

This difficulty is completely overcome according to the presentinvention by also compressing the excess material on the corners of thecontainer which has been filled into the chamber in the corner of thestationary guide element of the mold between its adjacent guide surfacesfor the dies. According to the invention this material is compressedinto the shape of a narrow strip or bar which extends along the cornerof the container and has the same solidity as the latter and ispreferably connected thereto only by a very thin web. After the finishedcontainer has been removed from the mold, this strip or bar may bebroken off completely along this thin connecting web.

The method according to the invention will hereafter be described indetail with reference to FIG. 2 which is again a horizontal sectionthrough the moldwhich is taken along the dot-and-dash line ll-ll of FIG.4 and shows an upright corner of the container. The walls of thecontainer are again designated by the numeral 1 and the stationary coreof the mold by the numeral 2. The two lateral dies 14 and 15 which aremovable in the directions of the arrows a and b are shown in their fullycompressed position. The dash lines 14' and 15' indicate the position ofthe pressure surfaces of the two dies in their retracted positions. Thedotted line 1 indicates like in FIG. 1 the position of the upper edge ofthe container walls l which is not visible in the drawings because it iscovered up by the dies 14 and in their compressing position.

The method according to the invention requires the lateral dies 14 and15 to be made of a width greater than that of the walls 1 of thecontainer to be molded. Consequently, the guide surfaces of eachstationary guide element 13 for the dies 14 and 15 are outwardly offsetby a distance x from the outer sur faces of the container walls 1. Thecorner between the two guide surfaces of guide element 13 is inclined atan angle of 45 so as to form a surface 3.3 which, however, isconsiderably narrower than the inclined surface 3' of the guide element3 of the previous mold as shown in H6. 1.

The upright corner of each die 14 and 15 between its surface which isslidable along the respective guide surface of guide element 13 and thepressure surface Ma or 15a which produces the outer surface of therespective container wall 1 is offset and inclined toward the rear (asseen with reference to the direction of the compression movement of eachdie) so as to form an inclined surface 17 or 13 between the lines whichare determined by the distance x, as mentioned above. Each of thesesurfaces 17 preferably extends at an angle of 45 to the adjacent guidesurface of the guide element 13, and when the I two adjacent dies 14 and315 are in the fully compressed or closed position as shown in FIG. 2,the adjacent surfaces 17 and 18 together with the inclined comer surface13' of guide element 13 enclose a narrow chamber 16. The adjacent edgesof the pressure surfaces Ma and 15a of the two dies which are to formthe upright corner between the container walls 1 are slightly chamferedso that, when the dies are in the fully closed position, a narrow slotremains which connects the chamber 16 with the edges of the pressuresurfaces 14a; Of course, what has here been said with reference to theupright comers of the mold parts l3, l4 and 15 for producing the uprightcorner between the container walls I as shown in MG. 2 is equallyapplicable to the other upright comers of the mold pans and corners ofthe container.

For carrying out the method according to the invention, the dies 14 and15 are first retracted so that their pressure sur' faces are in thepositions as indicated by the dash lines 14 and 15. The molding mixtureis then poured into the open mold. When the mold is then heated andclosed by moving the dies 14 and 15 toward the core 2 to the position asshown in H6. 2, not only that molding material will be compressed andcured which results in the container walls 1, but also the excessmaterial which is collected in the chamber .16 (as also indicated by thedot-and-dash line in FIG. 4 which then forms a solid strip or bar whichextends along the comer of the container between the walls 1 and isconnected to this comer by a thin web 19 which is formed as the resultof the chamfered upright edges of dies M and 15 at the ends of thepressure surfaces Ma and Ma adjacent to the inclined surfaces 117 and318. After the container walls ll including their strip-shaped cornerextensions l6 and the small intermediate webs 19 are fully compressedand cured, dies M and 15 are again retracted and the upper die 7 asshown in FlG. 4 is fully withdrawn whereupon the finished container withthe strips 16 thereon is removed from the mold in the direction verticalto the plane of FIG. 2. Strips 16 may then be broken off the uprightcorners of the container and, since this obviously occurs along theweakest part, namely, along the webs 19, the corners between theadjacent container walls 1 will be clean of any projections, except fora possible small burr on each corner which may be easily removed.

The problems which had to be solved regarding the upright corners of thecontainer in the manner as previously described also apply similarly tothe comers between the bottom and the sidewalls of the container. Whenthe loose material is filled into the mold and fills the space in whichthe sidewalls l as well as the bottom of the container are to be molded,there will also be excessive material along the comers between thebottom and sidewalls.

The conditions regarding these corners which prevail in the conventionalmethods of producing such containers will first be briefly describedwith reference to FIG. 3, in which the sidewalls of the container areagain designated by the numeral 1, the stationary core of the mold bythe numeral 2, and one of the lateral dies by the numeral 4, while thebottom of the container is designated by the numeral it). The lateraldies 4 are again movable in the direction of the double-arrow a, whilethe upper die 7 for the container bottom M) is movable vertically in thedirection of the double-arrow c. The container is therefore molded in anupside-down position. Dies and 7 are shown in their fully compressedposition, while the dash lines 4' and 7' indicate the pressure surfacesof these dies in their retracted positions. In order to be able to fillthe loose molding material from above into the mold and to remove thefinished container upwardly from the mold, the stationary guide ele ment8 for guiding the lateral dies 4 is set back as far from the adjacentlateral surface of die 7 as corresponds to the distance to which thelateral dies 4 may be retracted from their most forward positions. Thereis'thus a chamber 9 formed between the vertically moving die 7 and theguide element 8. At the end of the molding operation when the mold is inits completely closed position as illustrated in FIG. 3, this chamber 9will contain the excessive amount of material 9' which is not compressedbut cured by the heat of the mold and therefore has a loose crumblyconsistency. When the dies are then retracted, this crumbly materialfalls downwardly into the mold and must be carefully removed therefromin the same manner as described with regard to the material 6 adjacentto the lateral comers, as shown in FIG. 1. This again requiresconsiderable time and physical effort and entails the danger that thenext container will be defective if this waste material is notcompletely removed from the mold. Since the guide elements for thelateral dies must be laterally spaced from the upper die in order topermit the mold to be properly filled, these disadvantages occur notonly in the upside-down production of containers with inclined walls orwith walls with an outwardly projecting rim on its open end where theseguide elements might interfere with the removal of the finishedcontainer in the upward direction, but they occur also in the productionof containers with vertical and plane walls. Although on containers withsuch walls the excess material might possibly be compressed into thecorner portions between the container bottom and the sidewalls,this canbe done only on containers on which these corners are very rounded, butnever on containers with sharp corners.

In order to insure that this excessive material will be completelyremoved from the mold together with the finished container, theinvention further provides a procedure similar to that as alreadydescribed with reference to the upright corners between the sidewalls ofthe container. However, the operations of filling the mold and removingthe finished container require the parts of the dies for molding thecorners between the bottom md sidewalls of the container and thestrip-shaped outer extensions of these corners to be made of a differentshape.

One particular manner in which this part of the invention may be carriedout is illustrated by way of example in FIG. 4, in which the numeral 11again designates one of the sidewalls of the container, 2 designates thecore of the mold, and 10 designates the container bottom. The lateraldie 14 for molding the sidewall 1 and the vertically movable die 21 formolding the bottom 10 are illustrated in the fully compressing position,while the dash lines 14 and 21' indicate the retracted positions ofthese dies before the compressing operation. The horizontal guidesurface of the stationary guide element 22 of the mold and the uppersurface of the lateral die 14 which is slidable along this guide surfaceare parallel to and located above the plane of the intended uppersurface of the container bottom it) and spaced from this plane at adistance z. The vertical end surface of guide element 22 for the upperdie 21 is slightly offset toward the rear of a vertical projection ofthe outer edge 11 of the container wall, as indicated by the dotand-dashline 16 in FIG. 4 which corresponds to the outer edge of the strip 16 onthe upright corner of the container as shown in FIG. 2, so as to permitthe finished container to be lifted out of the mold past the guideelement 22 after the lateral die 14 has been retracted to the positionof the dash line 14 and the upper die 21 has been lifted completely outof the mold. The pressure surface of die 11 8 consists of a large lowerpart Ma and a short upper part 27. The lower part Ma serves forcompressing the sidewall l of the container and therefore has the sameshape and the same height as the outer surface of this wall up to thelevel of the upper surface of the container bottom 10. The short upperpart 27 of the pressure surface of die 14 above this level is recessedfrom the upper end of the lower part 14a for a distancey whichcorresponds substantially to the thickness to which the sidewall l is tobe compressed and it extends vertically to the plane of the uppersurface of the container bottom 10. Each lateral edge portion of theupper die 21 is step-shaped in accordance with the shape and therelative positions of the guide element 22, the upper end of the lateraldie 14 and the upper part 27 of the pressure surface of this die, andthe horizontal pressure surface Zla of the upper die 21. This horizontalsurface 210 of die 21 is adapted to compress the container bottom 10,while the vertical part 28 of the step forms an abutment on which thematerial which in the filling operation has been deposited in the area26 in front of the upper edge A of the retracted die 14 by the part 27of the pressure surface of die 14 so as to form a strip-shapedprojection 26 of the thickness y and a height equal to the height of thestep part 28. This strip-shaped projection is therefore compressed andcured to the same degree as the sidewall 1 and the bottom 10 of thecontainer. In order to prevent the strip 26 from being separatedentirely from the container during the simultaneous compressionmovements of dies 14 and 2!, the corner between the pressure surface 210of die 21 and its vertical part 28 is preferably slightly chamfered sothat, at the end of the compression movements of the dies a thinconnecting web 29 remains between the strip 26 and the corner betweeneach sidewall l and the bottom 10 of the container. After the lateraldies 14 and 15 have been retracted to their positions 14' and 15 and theupper die 21 has been fullyretracted from the mold and the finishedcontainer has then been lifted out of the mold, the projecting strip 26may be broken off the container bottom along the web 29 at the same timewhen the strips 16 are broken off the upright corners of the container,as described with reference of FIG. 2.

After the container has been removed from the mold, the mold is filledagain with the required amount of molding material and the upper die isthen lowered so that its pressure surface is in the position 21. Dies14, 15 and 21 are then moved toward the core 2 for the required distanceso as to compress and cure the material including that of the projectingstrips 16 and 26. When the material is fully compressed and completelycured, the upper die is again lifted out of the mold, whereupon thisfinished container may likewise be lifted out of the mold. Theprojecting strips l6 and 26 are then again broken off and any burrswhich might remain from the connecting webs l9 and 29 are removed.

Of course, the design of the mold as well as of the containers to bemade may be modified considerably. Thus, for example, it is possible tosimplify the mold by omitting the step-shaped outer edge portion of theupper die 21 so that the sidewall of this die.extends further upwardlyalong the dashline A and thus similarly as shown by the full line inFIG. 3, and the area 26' is then open in the upward direction. Althoughduring the compression of the dies the material in this area 26' maythen yield upwardly and will not be as highly compressed as the strip 26in the mold according to H6. 4, the rate of compression which is thenproduced will usually be sufficient to give the strip 26 a sufficientsolidity to be removed from the mold together with the container.

The mold according to the invention may also be designed so that,instead of projecting upwardly from the outer edges of the containerbottom 10, the strip 26 may project horizontally to the outside or evenobliquely similar to the strips M on the upright corners as shown inPEG. 2. if strip 26 is to project horizontally, guide element 22 and thelateral die l4 would extend to the level of the upper surface of thecontainer bottom 10 and the recess for molding the projecting strip 26may be provided either in the upper surface of the lateral die M or inthe lower surface of the upper die 21. Of course, the vertical guidewall of guide element 22 along which the upper die is slidable wouldthen have to be in a position so as also to permit the end of thehorizontal strip 26 to pass easily along this guide wall when thecontainer is being removed from the mold.

lf strip 26 is to project obliquely from the bottom corner of thecontainer, dies 14 and 21 would be designed similar to dies 14 and 15 asshown in FIG. 2, except that the vertical wall of guide element 22 wouldhave to be spaced from the vertical wall of die 21 similarly as shown inFlG. so that strip 26 could pass along guide element 22 when thefinished container is being removed from the mold.

As has previously been indicated, it is advisable to carry out thecompressing operation of all dies of the mold substantiallysimultaneously. if the compressing operation would be carried out in themanner as it was previously done, for example, by first moving only thelateral dies 14 and 25 toward the core 2, the same would occur asindicated in FIG. 3, namely, that the uppermost part of the material tobe compressed in the sidewalls 1 would partly escape in the upwarddirection so that within the area la a degree of compression wouldoccur, which is less than required, while thereafter when the upper die7 moves downwardly, the material which has previously escaped upwardlywould be partly compressed by this die together with the normal amountof material for the bottom 10 so that within the area 10a the materialwould be compressed excessively. The opposite results would occur if theupper die 7 would first carry out the compressing operation of thebottom 10 and the lateral dies 4 would compress the sidewalls 1thereafter. These conditions which did not become very apparent in themethods as previously carried out are, however, extremely important ifthe method is carried out according to the invention. If in this case,for example, the

lateral dies would first compress the material for the sidewalls of thecontainer, as shown in HO. 4, the material would partly escape from thesidewall l and the strip 26 toward the bottom corner, so that thedifierence in the compression ratio between the areas 1a and 10a wouldbe much more considerable. This, in turn means, that especially in thearea of the bottom corner which is subjected to strong stresses, thematerial would be very inhomogenous which would endanger the durabilityof the container. If, however, the production of the containers iscarried out in accordance with the invention by compressing and curingall parts of the containers simultaneously the material of eachcontainer will be very homogenous and the container will not have anyweak or overcompressed areas which may lead to its prematuredestruction.

If the containers to be produced should have absolutely smooth outercorners when they are removed from the mold, the connecting webs 19 and29 may also be omitted and these corners may be molded even withouthaving any burrs thereon. In this case, the adjacent dies of the moldare to be designed so as to meet at the respective corners. of thecontainer and to compress and cure the excessive material within thechambers in which the strips 16 and 26 are formed but in a manner so asnot to adhere to the corners by any connecting webs. When the moldingoperation is completed these separate strips may be either removed fromthe mold together with the container or separately therefrom withoutdanger that any residues might remain in the mold.

Although our invention has been illustrated and described with referenceto the preferred embodiments thereof, we wish to have it understood thatit is in no way limited to the details of such embodiments but iscapable of numerous modifications within the scope of the appendedclaims.

Having thus fully disclosed our invention, what we claim is:

1. A method of molding angular containers with an open top in anupside-down position of a nonflowing mixture of comminuted fibrousmaterials and a hot-setting binder comprising the steps of filling acertain amount of said mixture into the free areas of a mold between theouter wall surfaces of a stationary core corresponding to the innershape and dimensions of the desired containers and a plurality ofadjacent substantially horizontally movable lateral wall-forming diesand at least one substantially vertically movable upper bottom-formingdie when said dies are retracted from said core, each of said dies beingmovable in a different direction at substantially right angles to therespective outer wall surface of said core, and also filling a certainamount of said mixture into the free areas formed outside of the edgesof said core between said adjacent retracted dies, and then moving saiddies under heat and pressure toward said core so as to compress and curesaid mixture and thereby to form said container and also a strip ofsubstantially the same solidity as said container on the outside of atleast each upright edge of said container.

2. A method as defined in claim 1, in which said solid strip is alsomolded on the outside of the edges of said container between its bottomand sidewalls.

3. A method as defined in claim 1, in which each of said solid strips ismolded so as to be connected by a very thin web to the respective edgeof said container, and further comprising the steps of retracting saiddies and removing said molded container with said strips from said mold,and thereafter breaking off said strips along said thin webs.

4. A method as defined in claim 1, in which all of said dies are movedsubstantially simultaneously toward said core to compress and cure saidmixture.

5. A mold for producing angular containers with an open top in anupside-down position of a nonfiowing mixture of comminuted fibrousmaterial and a hot-setting binder comprising a core having outer sidesurfaces and a top surface corresponding to the inner shape anddimensions of the desired container; a plurality of adjacentsubstantially horizontally movable lateral wall forming dies, eachfacing a respective one of said side surfaces of said core and asubstantially vertically movable upper bottom-forming die facing saidtop surface of said core, each of said dies being movable in a directionat substantially right angles to the respective facing surface of saidcore, each of said lateral dies having a pressure surface of a greaterwidth than the respective sidewall of said desired container, each ofsaid pressure surface comprising a first part having dimensionssubstantially equal to those of the respective side wall and adapted tocompress and cure a sidewall of I said container, and a second partprojecting laterally beyond said first part and forming a cornerportion, said corner portion being rearwardly and outwardly inclinedwith respect to said first part and adapted together with the comerportion of the adjacent lateral die to compress and cure said mixturedeposited between said corner portions so as to form a strip of solidmaterial projecting obliquely and outwardly from an upright edge of thefinished container.

6. A mold as defined in claim further comprising an angular stationaryguide element between said adjacent lateral dies having guide surfacesfor guiding said lateral dies and having an upright edge at the frontend of said guide surfaces facing an upright edge of said core, saidedge of said guide element being chamfered so as to form a surface of awidth equal to the thickness of said strip and limiting the extentthereof in its outward direction from the respective upright edge ofsaid core and said container when said dies are moved toward said coreto compress said sidewalls and said strips.

7. A mold as defined in claim 5, in which each of said lateral dies hasa greater height than the sidewall of the container to be molded therebyand a main pressure surface of a height equal to the height of saidsidewall up to the level of the outer surface of said container bottomfor compressing and curing said sidewall and a shorter additionalpressure surface projecting above said level at least to the level ofthe uncompressed mixture filled into said mold when said dies areretracted, said additional pressure surface being recessed from theupper end of said main pressure surface by a distance substantiallyequal to the thickness of said compressed sidewall and extendingparallel to the adjacent lateral surface of said upper die and adaptedto compress and cure said mixture which has been filled into the areaabove said level on said lateral surface so as to form a strip-shapedprojection above said bottom level.

8. A mold as defined in claim 7, in which said upper die has a lateralwidth greater than the outer surface of said bottom to be molded and hasa pressure surface equal to the size of said outer bottom surface and alateral projection on each side of said pressure surface, saidprojection forming a step-shaped recessed edge portion first extendingupwardly from the end of said pressure surface for a distancesubstantially equal to the height of said additional pressure surface ofeach wallforming die and then substantially parallel to said pressuresurface of said upper die for a distance greater than the depth of therecess formed by said additional pressure surfaces.

9. A mold as define in claim 5, in which, when said lateral dies are intheir fully compressed position, the edge between said first and secondparts of said pressure surface of one of said dies engages with thecorresponding edge of the adjacent lateral die, whereby said stripmolded between said second parts of said'two lateral dies is severedfrom the upright edge of said container.

10. A mold as defined in claim 5, in which the edge between said firstand second parts of said pressure surface of each lateral die isslightly chamfered so that, when said lateral dies are in their fullycompressed position, said edges of two adjacent lateral dies are spacedat a very small distance from each other in which a thin web if formedwhich connects said strip to the upright corner of said container.

11. A mold as defined in claim 7, in which when said dies are in theirfully compressed position, the edge between said main pressure surfaceand said recessed additional pressure surface of one of said lateraldies engages with the outer edge of the adjacent pressure surface of theupper die whereby said strip-shaped projection is severed from the outeredge between said bottom and said sidewall.

12. A mold as defined in claim 7, in which the edge between said mainpressure surface and said recessedadditional pressure surface of one ofsaid lateral dies and the outer edge of the' adjacent pressure surfaceof the upper die are slightly charnfered so that, when said dies are intheir fully compressed position, said edges are spaced at a very smalldistance from each other in which a thin web is formed which connectssaid strip-shaped projection to the outer edge between said bottom andsaid sidewall.

iii. A mold as defined in claim 6, in which said pressure surface of atleast one of said lateral dies is outwardly and downwardly inclined froma plane coinciding with the outer surface of said bottom to be molded tothe free outer edge of said container, said chamfered upright edge ofsaid stationary guide element being disposed with respect to a verticalprojection of said free outer edge of said container so that, when saidcontainer has been molded and is lifted in the upper direction from saidmold when said dies are retracted, said outer edge of said containerwill slide freely passed said chamfered edge.

2. A method as defined in claim 1, in which said solid strip is alsomolded on the outside of the edges of said container between its bottomand sidewalls.
 3. A method as defined in claim 1, in which each of saidsolid strips is molded so as to be connected by a very thin web to therespective edge of said container, and further comprising the steps ofretracting said dies and removing said molded container with said stripsfrom said mold, and thereafter breaking off said strips along said thinwebs.
 4. A method as defined in claim 1, in which all of said dies aremoved substantially simultaneously toward said core to compress and curesaid mixture.
 5. A mold for producing angular containers with an opentop in an upside-down position of a nonflowing mixture of comminutedfibrous material and a hot-setting binder comprising a core having outerside surfaces and a top surface corresponding to the inner shape anddimensions of the desired container; a plurality of adjacentsubstantially horizontally movable lateral wall forming dies, eachfacing a respective one of said side surfaces of said core and asubstantially vertically movable upper bottom-forming die facing saidtop surface of said core, each of said dies being movable in a directionat substantially right angles to the respective facing surface of saidcore, each of said lateral dies having a pressure surface of a greaterwidth than the respective sidewall of said desired container, each ofsaid pressure surface comprising a first part having dimensionssubstantially equal to those of the respective side wall and adapted tocompress and cure a sidewall of said container, and a second partprojecting laterally beyond said first part and forming a cornerportion, said corner portion being rearwardly and outwardly inclinedwith respect to said first part and adapted together with the cornerportion of the adjacent lateral die to compress and cure said mixturedeposited between said corner portions so as to form a strip of solidmaterial projecting obliquely and outwardly from an upright edge of thefinished container.
 6. A mold as defined in claim 5 further comprisingan angular stationary guide element between said adjacent lateral dieshaving guide surfaces for guiding said lateral dies and having anupright edge at the front end of said guide surfaces facing an uprightedge of said core, said edge of said guide element being chamfered so asto form a surface of a width equal to the thickness of said strip andlimiting the extent thereof in its outward direction from the respectiveupright edge of said core and said container when said dies are movedtoward said core to compress said sidewalls and said strips.
 7. A moldas defined in claim 5, in which each of said lateral dies has a greaterheight than the sidewall of the container to be molded thereby and amain pressure surface of a height equal to the height of said sidewallup to the level of the outer surface of said container bottom forcompressing and curing said sidewall and a shorter additional pressuresurface projecting above said level at leaSt to the level of theuncompressed mixture filled into said mold when said dies are retracted,said additional pressure surface being recessed from the upper end ofsaid main pressure surface by a distance substantially equal to thethickness of said compressed sidewall and extending parallel to theadjacent lateral surface of said upper die and adapted to compress andcure said mixture which has been filled into the area above said levelon said lateral surface so as to form a strip-shaped projection abovesaid bottom level.
 8. A mold as defined in claim 7, in which said upperdie has a lateral width greater than the outer surface of said bottom tobe molded and has a pressure surface equal to the size of said outerbottom surface and a lateral projection on each side of said pressuresurface, said projection forming a step-shaped recessed edge portionfirst extending upwardly from the end of said pressure surface for adistance substantially equal to the height of said additional pressuresurface of each wall-forming die and then substantially parallel to saidpressure surface of said upper die for a distance greater than the depthof the recess formed by said additional pressure surfaces.
 9. A mold asdefine in claim 5, in which, when said lateral dies are in their fullycompressed position, the edge between said first and second parts ofsaid pressure surface of one of said dies engages with the correspondingedge of the adjacent lateral die, whereby said strip molded between saidsecond parts of said two lateral dies is severed from the upright edgeof said container.
 10. A mold as defined in claim 5, in which the edgebetween said first and second parts of said pressure surface of eachlateral die is slightly chamfered so that, when said lateral dies are intheir fully compressed position, said edges of two adjacent lateral diesare spaced at a very small distance from each other in which a thin webif formed which connects said strip to the upright corner of saidcontainer.
 11. A mold as defined in claim 7, in which when said dies arein their fully compressed position, the edge between said main pressuresurface and said recessed additional pressure surface of one of saidlateral dies engages with the outer edge of the adjacent pressuresurface of the upper die whereby said strip-shaped projection is severedfrom the outer edge between said bottom and said sidewall.
 12. A mold asdefined in claim 7, in which the edge between said main pressure surfaceand said recessed additional pressure surface of one of said lateraldies and the outer edge of the adjacent pressure surface of the upperdie are slightly chamfered so that, when said dies are in their fullycompressed position, said edges are spaced at a very small distance fromeach other in which a thin web is formed which connects saidstrip-shaped projection to the outer edge between said bottom and saidsidewall.
 13. A mold as defined in claim 6, in which said pressuresurface of at least one of said lateral dies is outwardly and downwardlyinclined from a plane coinciding with the outer surface of said bottomto be molded to the free outer edge of said container, said chamferedupright edge of said stationary guide element being disposed withrespect to a vertical projection of said free outer edge of saidcontainer so that, when said container has been molded and is lifted inthe upper direction from said mold when said dies are retracted, saidouter edge of said container will slide freely passed said chamferededge.